IRF6 Screening of Syndromic and a priori Non-Syndromic Cleft Lip and Palate Patients: Identification of a New Type of Minor VWS Sign.

Van der Woude syndrome (VWS), caused by dominant IRF6 mutation, is the most common cleft syndrome. In 15% of the patients, lip pits are absent and the phenotype mimics isolated clefts. Therefore, we hypothesized that some of the families classified as having non-syndromic inherited cleft lip and palate could have an IRF6 mutation. We screened in total 170 patients with cleft lip with or without cleft palate (CL/P): 75 were syndromic and 95 were a priori part of multiplex non-syndromic families. A mutation was identified in 62.7 and 3.3% of the patients, respectively. In one of the 95 a priori non-syndromic families with an autosomal dominant inheritance (family B), new insights into the family history revealed the presence, at birth, of lower lip pits in two members and the diagnosis was revised as VWS. A novel lower lip sign was observed in one individual in this family. Interestingly, a similar lower lip sign was also observed in one individual from a 2nd family (family A). This consists of 2 nodules below the lower lip on the external side. In a 3rd multiplex family (family C), a de novo mutation was identified in an a priori non-syndromic CL/P patient. Re-examination after mutation screening revealed the presence of a tiny pit-looking lesion on the inner side of the lower lip leading to a revised diagnosis of VWS. On the basis of this data, we conclude that IRF6 should be screened when any doubt rises about the normality of the lower lip and also if a non-syndromic cleft lip patient (with or without cleft palate) has a family history suggestive of autosomal dominant inheritance.

Orofacial clefting: update on the role of genetics.

INTRODUCTION: Cleft lip with or without cleft palate (CL/P) is one of the most common birth defects in the world. Prevalence varies between populations, with an average of 1/700. CL/P has a major clinical impact, requiring surgical, dental, orthodontic, speech, hearing and psychological management throughout childhood. The aetiology of CL/P is mostly unknown, and it is thought that both genetic and environmental factors play a role. Several causative genes for inherited syndromic forms of CL/P have been identified, and some recent studies have shown that these genes also contribute to the occurrence of isolated forms. Van der Woude syndrome (VWS) is one of the best models for non-syndromic CLP. It is an autosomal dominant disorder characterised by the presence of pits on the lower lip in addition to CL/P. Pits are the only feature distinguishing VWS from isolated clefts. Interestingly, in numerous VWS patients, the lip pits are very small and not readily diagnosed, thus mimicking isolated CL/P. Mutations in the IRF6 gene were shown to be the major genetic cause of VWS.' RESULTS: We performed direct sequence analysis of IRF6 on samples from a large European cohort and identified mutations in 27 (80%) families. This shows that IRF6 is the major causative gene of VWS in Europe also. Moreover, it is the gene to study when a seemingly isolated CL/P patient has minor signs, such as lip pits, since the identification of a mutation in IRF6 is associated with an increase in the risk of having a child with CL/P from 4-6%, the risk of transmission of an isolated cleft, to 50%, the risk of transmission of a dominant Mendelian disorder like VWS. Moreover, we studied the association of isolated CL/P with the IRF6 locus using two variants in a set of 195 patients from Belgium. As in an American study, a clear association was observed. This suggests that IRF6 also contributes to the occurrence of sporadic, isolated CL/P, even if no mutation in the gene can be identified in such patients. CONCLUSION: In conclusion, genes that are mutated in familial syndromic forms of CL/P may be predisposing genetic factors to sporadic isolated CL/P. Due to technological advances and the availability of the human genome sequence, we have now the opportunity to try and unravel the genetic factors behind the various forms of CL/P.

Four common glomulin mutations cause two thirds of glomuvenous malformations ("familial glomangiomas"): evidence for a founder effect.

BACKGROUND: Glomuvenous malformation (GVM) ("familial glomangioma") is a localised cutaneous vascular lesion histologically characterised by abnormal smooth muscle-like "glomus cells" in the walls of distended endothelium lined channels. Inheritable GVM has been linked to chromosome 1p21-22 and is caused by truncating mutations in glomulin. A double hit mutation was identified in one lesion. This finding suggests that GVM results from complete localised loss of function and explains the paradominant mode of inheritance. OBJECTIVE: To report on the identification of a mutation in glomulin in 23 additional families with GVM. RESULTS: Three mutations are new; the others have been described previously. Among the 17 different inherited mutations in glomulin known up to now in 43 families, the 157delAAGAA mutation is the most common and was present in 21 families (48.8%). Mutation 108C-->A was found in five families (11.8%), and the mutations 554delA+556delCCT and 1179delCAA were present together in two families (4.7% each). Polymorphic markers suggested a founder effect for all four mutations. CONCLUSIONS: Screening for these mutations should lead to a genetic diagnosis in about 70% of patients with inherited GVM. So far, a mutation in glomulin has been found in all GVM families tested, thus demonstrating locus homogeneity.